Recently, an in-vehicle image recognizer has been in practical use. Such an in-vehicle image recognizer observes a surrounding area of a vehicle by a vehicle-mounted camera, detects a position of another vehicle, a position of a lane marker, or the like from the observed image, and determines the possibility of contact with another vehicle or the possibility of lane departure based on the detected position of another vehicle or the detected position of the lane marker, so as to alert a driver.
In such a system, while a vehicle is traveling in rain, water splashed by a vehicle may be attached to the lens surface of the camera. Also, while a vehicle is traveling on a dirt road, dust stirred up by the vehicle may be attached to the lens surface of the camera. Further, while a vehicle is traveling on a road on which a snow-melting agent is spread, the snow-melting agent splashed by the vehicle may be attached to the lens surface of the camera. These substances attached as described above are dried, and impurities in water, dust, or snow-melting agent are deposited, and accumulate on the lens surface to cause grime (hereinafter, white turbidity) on the lens surface.
When a white turbidity part is generated on the lens surface, light entering the lens is scattered at the white turbidity part and therefore blurring or bleeding occurs in the observed image. Since the contrast of the image of another vehicle or the lane marker which is a detection target is lowered due to such blurring or bleeding, lack of detection or false detection of another vehicle or a lane marker may occur. Due to the occurrence of lack of detection or false detection, an appropriate alert regarding the position of another vehicle or the position of the lane marker may not be provided to a driver.
In a system in which a crew in a vehicle cannot visibly recognize an image obtained by a camera, the crew cannot confirm that a lens has a white turbidity part, and the above-described lack of detection or false detection therefore gives the crew a sense of uncertainty with the system.
In order to prevent such lack of detection or false detection, for example, an obstacle detector for a vehicle is disclosed (for example, Patent Literature 1).